Currently, various electronic products are quickly developed to have largely reduced weight and dimensions but high operating performance, frequency and speed. As a result, more and more heat is produced by the electronic products during operation thereof to even have adverse influence on the products' reliability and service life. Therefore, heat dissipation has become a very important issue for all kinds of electronic products. Among others, cooling fan is frequently used as a heat dissipation device. And, to obtain enhanced heat dissipation performance, a plurality of serially connected fans can be used to produce airflow of increased volume and pressure.
Generally, two fans are serially connected to form a serial fan structure. Each of the two fans includes, for example, a fan wheel, a frame, a stator, a Hall sensor, a micro control unit (MCU) and a circuit board; and the Hall sensor, the MCU and a plurality of other electronic circuits, such as a buck circuit, a voltage regulation circuit and a pulse width modulation (PWM) circuit, are plugged into the circuit board. In addition, a coil assembly on the stator for each fan is always electrically connected to the circuit board of the same fan. To achieve the purpose of cost control, most fan manufacturers would generally use low-specification parts for low-power serial fan structure.
However, the use of low-specification parts to achieve cost control in manufacturing the conventional serial fan structure causes another problem. In each fan, there are parts having low use rate, such as the buck circuit, the voltage regulation circuit and the PWM circuit. Since these low-use-rate parts provide some necessary functions, they should and could not be omitted from the fan. Without omitting the low-use-rate parts, the use of low-specification parts can only achieve very limited fan manufacturing cost reduction. Therefore, the fan manufacturers have to work out other effective ways for further reducing the fan manufacturing cost.
It is therefore tried by the inventor to develop an improved integrated system of circuits for serial fan structure, in order to overcome the above-mentioned problems and disadvantages as found with the conventional serial fan structure